The invention relates to a vehicle wheel comprising a rim designed to be mounted for rotation and a pneumatic tire detachably mounted on the rim. The tire has a body which is of torus shape in cross-section and which has a roughly cylindrical running surface or tread as well as two radially extending side walls and at the edges next to the rim it has seatings or beads reinforced by inextensible bead wires, the beads being designed to be arranged and secured between flanges on the rim.
Currently in vehicle wheels the pneumatic tire acts as that structural element which has to transmit all the forces in use from the vehicle to the road and vice versa. Accordingly the endeavours of the manufacturer are concentrated on optimizing the tire, in particular with regard to its characteristics in use, namely the handling, the rolling resistance, the co-efficient of friction between the tire and the road surface, comfort and wear, if possible without forfeiting advantages and qualities already achieved.
Vehicle wheels of this kind are currently known and normal in vehicles of all kinds, in particular in motor vehicles and associated trailers.
In recent years development has been concentrated on finding improvements in pneumatic tires, and in particular in the breakers or reinforcements of them. As a result impressive improvements in tires have also been achieved,
This concentration of the development efforts on the breaker and running surface area of the tires which are known and used at the present day does, however, leave neglected the fact that also the structurally stiffened so-called chafer strips, which are present in the side walls radially above the beads at about the level of the carcass plies, are subjected to "working" at a high frequency as a consequence of the lateral bulging initiated by the peripheral disturbance in the contact area, but also in the region of so-called chafer strips or standing wave and the enlargement of radius over the whole unloaded periphery caused by tangential displacement action of a reinforcement belt or breaker which is stiff against expansion and compression, and therefore, by absorbing driving energy they add quite substantially to the rolling resistance of the tire.
This problem cannot be overcome or influenced by improvements to the breaker. All the improvements achieved hitherto in the rolling resistance of the tire have in practice only been achieved by improvements in the breaker and running surface regions.
In particular up to now too little account has been taken of the fact that the tire is only one part of the wheel system and the rim on which the tire is mounted is the other part of this wheel system.
Despite all efforts in design and in specific materials aimed at stiffening the base wall or chafer strip region, the currently orthodox chafer strips de form under the effect, during use, of up to 100 changes of flexing load per second and thereby they develop--according to the design and the operating conditions--30 to 50% of the overall rolling resistance of the tire. In addition to this spectacular deformation work from the wheel load and the side forces the stiffened chafer strips are permanently loaded during use by the toe-in and the camber of the wheel.
This more inconspicuous working of the chafer strip regions is indeed overshadowed by the working from wheel load and side forces, yet it does consume an avoidable specific fraction of the driving energy.